Sheet metal rotors for compressors and turbines



Aug. 30, 1960 E. A. STALKER SHEET METAL RO'I'ORS FOR COMPRESSORS AND TE'RBINES Filed Oct. 13, 1954 IN V EN TOR.

SHEET METAL ROTORS FGR COMPRESSORS AND TURBHJES Edward A. Stalker, Bay City, Mich, assignor to The Stalker Corporation, a corporation of Michigan Filed Oct. 13, 1954, Ser. No. 461,969

4 Claims. (Cl. 230-134) An object of the invention is to provide a means of securing blades to a rotor hub where either or both parts are of sheet metal construction.

Other objects will appear from the description, drawings and claims.

,The above objects are accomplished by the means illustrated in the accompanying drawings in which Fig. 1 is a fragmentary axial section of a rotor;

Fig. 2 is an axial view of a portion of a rotor near its Fig. 3 is a section through the blades on line 33 in Fig. 1;

Fig. 4 is a fragmentary section on line 44 in Fig. 1;

Fig. 5 is a fragmentary view of an end of a blade stem;

This invention relates to compressors and turbine rotors employing sheet metal construction.

Fig. 6 is a section of a blade stem on line 66 in Fig. 5, and

Fig. 7 shows an alternate means of replaceably fixing a blade stem in the hub structure, namely by remeltable solder.

Hollow sheet metal blades are light and econorm'cal to produce but present certain problems of attachment to the rotor hub structure if the blades are to be readily replaceable. The attachment should also be light to preserve the saving in weight of the hollow blade. Yet the attachment must be able to withstand vibration and fatigue at high rates of rotor rotation.

The blades of this invention are for compressors and turbines of the axial flow type.

This invention includes compressor rotors for increasing the static pressure and density of an elastic fluid. In order to achieve a significant change in density with an axial flow compressor each rotor must be operated at a speed high enough to effect a significant change in density, that is a change which in magnitude is outside the usual order of engineering accuracy in industry. Thus machines are considered to be compressors as distinguished from fans or blowers at tip speeds of about 400 feet per second or more. At such a speed the average change in density along the blade length is about 3% which is just about the common order of accuracy of measurement of the density. Such compressors are expected also to operate at blade tip speeds close to the velocity of sound. At such speeds the change in pressure may be more than 70% or more than 10 pounds per square inch for air inducted at atmospheric pressure.

Since in a compressor and turbine rotor there is a substantial pressure variation from front to rear the ratio of the hub radius to the blade tip radius is relatively large of a value of the order of 0.5 and preferably greater so that the pressure difierence between front and rear sides can be sustained without a return flow at the hub such as occurs in a fan. For the same reason the blades are spaced peripherally close together, preferably about one chord length or less apart.

Commonly half to all the pressure rise occurs in the rotor between the leading and trailing edges. To susatent ire from leading to trailing edges of the blades the hub rim between adjacent blades and from leading to trailing edges is a fair and continuous surface. Also at all rotative speeds the case must fit closely about the blade tips which are contoured to the cylindrical surface of the case along substantially the whole length of the blade chord.

To diffuse the flow between blades to achieve a pressure rise the flow should follow the blade surfaces without eddies. Accordingly the blades should have rounded leading edges. They should have sharpened trailing edges to be efiicient.

Because of the limited weights of the blades and the rim means the disk can have a limited thickness of the order of 0.003 times the wheel maximum diameter (tip diameter) or less. Thus rather large disks can have a thickness less than 0.050 of an inch. These would be costly and difiicult to machine. The blades and rim means may have wall thicknesses less than the disk thickness.

it is commonly understood in engineering and industry that sheet metal construction is limited to sheets whose planar dimensions are large in comparison to their thicknesses for thicknesses less than about 73 of an inch. Sheets of greater thickness are called plates. (Steel sheet and plate manufacturers list their product of large planar dimensions of A or less as sheets and greater thicknesses as plates.) Sheet metal constructions are comprised of parts which are cut out from sheet material and require cutting which is chiefly limited to defining the contours of the part in the plane of the sheet, or to such parts wln'ch are subsequently given another shape. by pressing with a die.

Referring now to the drawings the rotor is indicated generally as 10 in Figs. 1-3 and comprising a plurality of blades supported in the rotor hub structure.

The hub structure comprises the rim 18 fixed to the rotor disk 20, the channel shaped rib parts 22 and 24 fixed to and in faying relation with opposite side faces of the disk with axially directed flanges thereon opening outwardly, and the toothed clutch 28 which is a ring encircling the axis of rotation which is not shown. The ring has the teeth 30, and the flange 32 to which the disk 20 is fixed preferably by welding and soldering.

Each blade is comprised of a blade envelope 40 enclosing a blade Stem which comprises two stem parts 44 and 45. These are spaced apart at their inner ends vbut are fixed back to back in the blade as shown in Figs.

1 and 3. The envelope is preferably brazed to the sides of the stem parts.

The stem parts 44 and 45 are reduced in chordwise length so that each becomes an open channel shown in Fig. 4. Each stern channel or part fits closely within the recess of one of the ribs 2224, each of which is also preferably of channel construction Thus ,in Fig. 4 the stem part 44 fits into the rib 22 and stem part 45 fits into rib 24, the respective rib and stem flanges thus being in faying contact over a substantial radial extent. The stem parts are joggled to align them with the ribs and are preferably riveted to the sides and back of the ribs as shown in Fig. 4 by rivets 50 and 52. In replacing a blade the rivet heads are sheared off and new rivets are used for installing another blade. Bolts might also be used instead of the rivets but they are heavier and require locking devices which add to the weight.

The rivet type of joint provides adequate strength and in conjunction with the nesting channel arrangement reduces fretting of the metal to a minimum. This is important since the blades normally have a high rate of vibration during rotation of the rotor which causes fretting away of the metal where two surfaces fay. Such Wearing away leads to surface indentations at which fatigue failure can begin by developing a crack. The type of joint of this invention excludes this type of failure over a long length of useful life of the rotor.

In place of rivets, solder could also be used to fix the stern parts in the ribs. The solder should be one melting at a lower temperature than the solder used for joining the other structural members like the ribs to the disk. It also should be low enough so that the heat treat ment of the parts is not adversely affected. For instance if copper is used to solder the main structural parts together, a silver solder melting at a temperature of about 1100 F. could be used for the joints between ribs and stems. Remeltable solder fixes the stem to the rib in Fig. 7 so that each blade is replaceable.

The rim comprises the outer ring 60 and the front and rear inner rings 62 and 64 respectively. The latter are fixed to the outer ring at its flanges 7t) and 72. The inner ends of the inner rings are soldered to the rotor disk 20 at 74 and 76, respectively.

The blade envelopes are inserted radially inward through openings 78 in the outer rim.

Preferably socket parts 90 on each side of a blade support some of the lateral bearing load of each blade. These socket parts are fixed to the rim by suitable flanges.

It will now be clear that I have disclosed a novel removable means for securing blades in a rotor where one or both are of sheet metal, and this means is light, economical and adapted to resist vibration failures.

While I have illustrated specific forms of the invention, it is to be understood that variations .may be made therein and that I intend to claim my invention broadly as indicated by the appended claims.

I claim:

1. In combination in an axial flow bladed rotor, a hub structure including a radially extending sheet metal disk, a sheet metal channelshaped rib member fixed to and laying the side face of said disk over a major portion of its radial extent and extending outwardly thereof in a generally radial direction, said disk being peripherally continuous throughout said faying area, said rib member having an axially directed flange thereon, a sheet metal blade stem interfitting with and projecting radially outwardly from said rib member, said stern faying with said flange of said rib member over a substantial radial extent, means for securing said blade stems in position upon said rib members, and sheet metal rim means secured to said disk and extending from blade to blade in the peripheral direction.

2. In combination in an axial flow bladed rotor, a hub structure including a radially extending sheet metal disk, a sheet metal rib member having a fiat face positioned at one side of and -faying said disk over a substantial area, said member being bonded to the side face of said disk and extending outwardly thereof in a generally radial direction, said disk being peripherally continuous throughout said faying area, said rib member having an axially directed flange thereon, a sheet metal blade stem interfitting with said flange and projecting radially outwardly from said rib member, said stem having a fiat face faying with said flange of said rib member over a substantial radial and axial extent, means for securing said blade stems in position upon said rib members, rim means secured to said disk and extending from blade to blade in the peripheral direction, and blade envelopes received over said blade stems and extending radially inwardly through said rim means.

3. In combination in an axial flow bladed rotor, a hub structure including a radially extending sheet metal disk, sheet metal rib members having a flat face faying with and fixed to opposite side faces of said disk over a substantial area and extending outwardly thereof in a generally radial direction, said disk being peripherally continuous throughout said faying area, said rib members each having an axially directed flange thereon, sheet metal blade stems interfitting with and projecting radially outwardly of said rib members, each said stern having a flat face laying with a corresponding flange of one of said rib members over a substantial radial and axial extent, means for securing said blade stems in position upon said rib members, and rim means secured to said disk and extending from blade to blade in the peripheral irection.

4. In combination in an axial flow bladed rotor, a hub structure including a radially extending sheet metal disk, sheet metal rib members having a fiat face faying with and fixed to opposite side faces of said disk over a substantial area and extending outwardly thereof in a generally radial direction, said disk being peripherally continuous throughout said faying area, said rib members each having an axially directed flange thereon, sheet metal blade stems interfitting with said flanges and projecting radially outwardly of said rib members, each said stem having a fiat face faying with a corresponding flange of one of said rib members over a substantial radial and axial extent, means for securing said blade stems in position within said flanges, rim means secured to said disk and extending from blade to blade in the peripheral direction, and sheet metal blade envelopes received over said blade stems and extending radially inwardly through said rim means.

References Cited in the file of this patent UNITED STATES PATENTS 913,273 Emden Feb. 23, 1909 2,189,252 Seggio Feb. 6, 1940 2,497,151 Clark et al Feb. 14, 1950 2,601,969 Eastman July 1, 1952 FOREIGN PATENTS 138,839 Australia Sept. 26, 1950 322,077 France Jan. 27, 1903 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noe 2350 858 August 30, Edward As Stalker It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, lines 29 and 30 strike out "This invention relates to compressors and turbine rotors employing sheet metal construction," and insert the same before line 15 as the first paragraph of column 1.,

Signed and sealed this 4th day of April 1961.,

(SEAL) Attest: ERNEST W. SWIDER XXfiiii-IIQ ARTHUR w. CROCKER Attesting Oificer I Acting Commissioner of Patents 

